Traditionally, outdoor shooting ranges utilize dirt berms to provide side ballistic protection. Although dirt berms are used effectively in this application, they have a number of disadvantages. First, dirt berms must have a 2:1 compacted slope. This means that for every foot of height, the berm must be 2 feet wide. A 16 foot high dirt berm must be 32 feet wide, which occupies a considerable area. Given that two berms are required for sidewall protection, this means that 64 feet must be devoted to the berms alone. Another consequence is the range takes significant time and expense to construct. Furthermore, considerable ongoing expense occurs because the berms must be erosion controlled, periodically the lead projectiles must be removed, and the berms must be re-compacted. These maintenance activities also prevent the range from being used while they occur. Finally, dirt berms have no acoustical absorption value.
Concrete walls or concrete masonry walls are a space-saving alternative to dirt berms that provide similar ballistic protection. However, concrete walls require a substantial footing or foundation because they are heavy. The type of foundation is determined by the wall's height, the wind load, the soil density, and the seismic zone. A standard 16 foot wall designed for a standard 70 mi./h. Wind load in a low seismic zone with normal 2,000 pound density soil requires a foundation approximately 8 feet wide and 3 feet deep. This design increases cost substantially and requires a 28 day cure time. In addition, in order to provide ballistic protection, a minimum of 5,000 PSI concrete is required, which further adds to the wall's cost. This design is time-consuming to construct and much more expensive than dirt berms. Concrete surfaces have no acoustical absorption; instead, they reflect gunfire sound levels. Gunfire sound levels easily reach levels of 145-165 dBA. This energy is reflected off parallel concrete surfaces, in this case the two side walls, which will reflect this gunfire sound level for as long as 8 seconds. This reflected sound level, when added to the actual gunfire sound level, produces very high, unhealthy sound levels that will carry for a length of over ¾ of a mile. This sound level can be very intrusive to neighbors or adjacent buildings within this ¾ mile radius.
Therefore, a need exists for a new and improved ballistic wall that provides ballistic protection with a small footprint, eliminates lead remediation, and absorbs the gunfire sound level. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the sound absorbing wall according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of providing ballistic protection with a small footprint and eliminating lead remediation.